Download 150Lecture 8 A/C and Voltage, Power Lecture Notes Page

FOWLER CHAPTER 8
LECTURE 8 ALTERNATING
CURRENT AND VOLTAGE
CHAPTER 8 AC AND VOLTAGE P.201
FOR A DC WAVEFORM IN A SIMPLE CIRCUIT THE OUPUT IS ALWAYS CONSTANT, EXCEPT WHEN
THE CIRCUIT IS SWITCHED ON/OFF. DC WAVEFORMS CAN BE + OR - BUT NEVER BOTH.
V
+
-
t
TYPES OF AC WAVEFORMS
SINUSOIDAL
MOST COMMONLY USED IN
DIGITAL ELECTRONICS
SAWTOOTH( TV,RADAR)
CYCLE P.203: ONE WAVEFORM THAT DOES NOT REPEAT ITSELF
½ CYCLE
.25 S
PERIOD (T) : TIME TO COMPLETE ONE CYCLE.( IN THIS CASE .25 SECONDS)
SAME THING
FREQUENCY( f ) : # OF CYCLES/SECOND
Time (sec) FOR THIS WAVEFORM f = 1 CYCLES/SEC
HERTZ: UNIT OF FREQUENCY . FOR THE ABOVE WAVEFORM f = 1 Hz
f =1/T OR f =1/λ
AMPLITUDE: (a) HEIGTH OF THE
WAVEFORM.
EXAMPLE: FIND THE FREQUENCY FOR THE WAVE FORM BELOW.
=1/T = 1/20ms = 1/.002 = 500Hz
PEAK VP : MAX. VALUE OF WAVEFORM.
CAN BE EITHER + OR-
VPP  2VP
SINCE WAVEFORMS ARE NOT CONTINIOUS AT
ALL TIMES THE AVERAGE VALUE IS USED.
VAV =AVERAGE VALVE
VAV =0.637VP
USEFUL IN AC/DC CIRCUITS
VP = 1.57VAV
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M/U#38 3:30-12:40
http://www.youtube.com/watch?v=7QCxbwzikFk
RMS( ROOT-MEAN-SQUARE)
WHAT IS THAT? 1. WAVE FORM IS DIVIDED UP INTO SMALL INTERVALS.
2. EACH INTERVAL IS SQUARDED.
3. MEAN (AVERAGE) OF SQUARED VALUE IS FOUND.
4. SQUARE ROOT OF THE MEAN IS CALCULATED.
\
RMS value is an equivalent DC value which tells you how many volts or
amps of DC that a time-varying sinusoidal waveform is equal to in terms
of its ability to produce the same power. For example, If you have mains
supply of 240Vac and is assumed an effective value of “240 Volts RMS”.
This means then that the sinusoidal RMS voltage from the wall sockets of
a home is capable of producing the same average positive power as 240
volts of steady DC voltage as shown below.
rms voltage = 0.707 peak voltage
rms voltage = 1.11 average voltage
peak voltage = 1.414 rms voltage
peak voltage = 1.57 average voltage
average voltage = 0.637 peak voltage
average voltage = 0.9 rms voltage
SINE WAVES
REVIEW: WHEN A CONDUCTOR MOVES THRU A MAGNETIC FLUX, A
VOLAGE AND CURRENT ARE INDUCTED IN THE CONDUCTOR.
THE AMOUNT OF INDUCED VOLTAGE IS A
FUNCTION OF THE AMOUNT
OF FLUX CUT BY THE CONDUCTOR
Magnetic Induction in a Wire
http://www.youtube.com/watch?v=P3kJd3MDeuk&list=UUOc
3q8ChcDYyeyFROxLDhuw
AMOUNT OF FLUX CUT DEPENDS ON
1. SPEED OF THE CONDUCTOR
2. FLUX DENSITY
3. ANGLE THAT CONDUCTOR CROSSES THE MAGNETIC FILED.
SEE FIG. 8.8,P208
DIRECTION OF INDUCTED CURRENT DEPENDS ON
1. DIRECTION CONDUCTOR IS MOVING.
2. POLARITY OF THE MAGNETIC FIELD.
LEFT HAND RULE. P.209
Building a Generator: size of induced current
http://www.youtube.com/watch?v=KUrMt6ic53o&list=UUOc3
q8ChcDYyeyFROxLDhuw
PRODUCING SINE WAVES. P.209
YOU CAN GENERATING A SINE WAVE BY
ROTATING A CONDUCTOR THRU A MAGNETIC
FIELD.
Commutators: Basics on AC and DC Generation
http://www.youtube.com/watch?v=ATFqX2Cl3w&list=UUOc3q8ChcDYyeyFROxLDhuw&index=6
Slip Rings and Brushes - Generators
http://www.youtube.com/watch?v=P83Qa3Chb7I&list=UUOc
3q8ChcDYyeyFROxLDhuw
ONE ROTATION OF A CONDUCTOR THRU 4 POLES
GENERATES TWO CYCLES OF VOLTAGE/CURRENT.
YOU TUBE:AC Motor Animation Video
http://www.youtube.com/watch?v=Q4FlUP-kJe8
TO MAKE A AC GENERATOR YOU NEED THE FOLLOWING
PARTS: WINDINGS,MULTILOOPED COIL.
ARMATURE: WINDING WOUND ON A SILICON STEEL CORE.
SLIP RINGS (COMMUTATORS)
BRUSHES
FIELD COILS
YOU TUBE,How generator works by Khurram Tanvir
http://www.youtube.com/watch?v=i-j-1j2gD28
OUTPUT OF A GENERATOR DEPENDS ON
1. # OF TURNS IN THE ROTATING COILS.
2. SPEED THAT THE COILS ROTATE.
3. FLUX DENSITY OF THE MAGNETIC FIELD.
YOU TUBE:AC Generator Action.avi
http://www.youtube.com/watch?v=mCvXa_VVFh4
GENERATOR FREQUENCY P.212
FREQ. OUTPUT OF A GENERATOR DEPENDS ON
1. # OF PAIRS OF MAGNETIC POLES.
2. ROTATIONAL SPEED OF THE COILS.
FREQ. GEN.OUT =(R PER MINUTE)X(PAIRS OF POLES)/60
EXAMPLE:WHAT IS FREQ. OF 6 POLE GENERATOR ROTATING AT 1200 RPM?
RN 1200  6
f 

 120c / s  120 Hz
60
60
WHERE R  ROTATIONAL SPEED
N  NUMBER OF POLES
AC GENERATOR BUILT IN 1890
YOU TUBE,Magnetism: Motors and Generators START AT 25SEC
http://www.youtube.com/watch?v=d_aTC0iKO68
The Frequency of an AC Generator www.wisc-online.com/ViewObject.aspx?ID=IAU14108
Advantages of A.C. over D.C. / Why generation is done in A.C.
1. AC CAN BE GENERATED AT HIGH VOLTAGES.
2. HV AC GENERATORS ARE SIMPLER AND CHEAPER THEN DC GENERATORS.
3. AC CAN BE STEPPED UP OR DOWN WITH TRANSFORMERS.
The Mechanical Universe - 38 - Alternating Current,17:00-21:00 AC vs.DC
http://www.youtube.com/watch?v=7QCxbwzikFk
50Hz vs. 60Hz
Utility Frequencies in Use in 1897 in North America
Hz
Description
140
Wood arc-lighting dynamo
133
Stanley-Kelly Company
125
General Electric single-phase
66.7
Stanley-Kelly company
62.5
General Electric "monocyclic"
60
Many manufacturers, becoming "increasingly
common" in 1897
58.3
General Electric Lachine Rapids
40
General Electric
33
General Electric at Portland Oregon for rotary
converters
27
Crocker-Wheeler for calcium carbide furnaces
25
Westinghouse Niagara Falls 2-phase - for operating
motors
Utility Frequencies in Europe to 1900
Cycles
Description
133
Single-phase lighting systems, UK and Europe
125
Single-phase lighting system, UK and Europe
70
Single-phase lighting, Germany 1891
65.3
BBC Bellinzona
60
Single phase lighting, Germany, 1891, 1893
50
AEG, Oerlikon, and other manufacturers, eventual
standard
48
BBC Kilwangen generating station,
46
Rome, Geneva 1900
45 1/3
Municipal power station, Frankfurt am Main, 1893
42
Ganz customers, also Germany 1898
41 2/3
Ganz Company, Hungary
40
Lauffen am Neckar, hydroelectric, 1891, to 1925
38.6
BBC Arlen
25
Single phase lighting, Germany 1897
3 PHASE AC P.213
POWER PLANTS PRODUCE 3 PHASE AC. EACH PHASE IS SEPARATED BY 120°. P. 214
3 Phase AC Motor Working Principle
http://www.youtube.com/watch?v=fGPdPKMSpv8
(b) Output waveform (red) for three cycles of a
200 Vp-p input to a single-phase half-wave rectifier
(a) Output waveform (red) for three cycles of a
200 Vp-p input to a three-phase half-wave rectifier
Fig. 8-24 P.220 A comparison of half-wave rectification
of single-phase and three-phase ac.
(a) Output waveform of a full-wave singlephase rectifier with an input of 200 Vp-p.
(a) Output waveform of a full-wave threephase rectifier with an input of 200 Vp-p.
Fig. 8-25 P.221 Comparison of full-wave rectification
of three-phase and single-phase ac.
3 PHASES ARE CONNECTED SO THE LOAD CAN BE CARRIED ON 3 CONDUCTORS FROM
THE POWER PLANT TO THE USER.
3 PHASES ARE CONNECTED IN EITHER DELTA OR WYE CONFIGURATION.
120/208 3-Phase Wye: 208 volts are present
between all 3 phases. 120 volts between all 3
phases to Neutral
3 PHASE 120/208V, 4 WIRE WYE SYSTEM
LINE 1
120 V
PHASE 1
120 V
208 V
NEUTRAL
PHASE 3
120 V
PHASE 2
120 V
120 V
TO 3 PHASE
LOADS
208 V
LINE 2
GROUND
120 V
208 V
LINE 3
UNDER LOAD:LINE AND PHASE CURRENTS ARE NOT EQUAL.
SINCE 2 PHASE VOLTAGES ARE SEPARATED BY 120º , THEY CANNOT BE ADDED TOGETHER
ILINE = 1.732IPHASE
VLINE = 1.732VPHASE
VLINE2 = 1.732(120V) = 208V
SINGLE PHASE 120 V ARE CONNECTED BETWEEN THE NEUTRAL AND ANY ONE LINE.
SINGLE PHASE 208 V CIRCUITS ARE CONNECTED BETWEEN ANY 2 OF THE 3 LINES.
3 PHASE 208 V ARE CONNECTED ACROSS 3LINES.
ADVANTAGES OF 3 PHASE (Φ) SYSTEMS.
1.MORE EFFICENT USE OF COPPER.
2 PROVIDES A MORE CONSTANT LOAD ON THE GENERATOR.
3. MOTORS ARE LESS COMPLEX
4. 2 OUT OF 3 PHASES ARE PROVIDING CURRENT AT ANY TIME.
VARIOUS 3 PHASE TRANSFORMERS
ELECTRIC CARS HYBRIDS AND PLUG IN HYBRIDS
CHARGING A ELECTRIC CAR USING MAGNETIC INDUCTION
INDUCTION COILS CHARGING A ELECTRIC CARS BATTERY PACK
ONE OF THE MANY PRESENT DAY PLUG AND SOCKET FOR ELECTRIC CARS
Leviton Evr-Green Base Level 1 GFCI Guide Light Receptacle for Electric Vehicles
Charging time
Power supply
Voltage
Max current
6–8 hours
Single phase - 3,3 kW
230 VAC
16 A
2–3 hours
Three phase - 10 kW
400 VAC
16 A
3–4 hours
Single phase - 7 kW
230 VAC
32 A
1–2 hours
Three phase - 24 kW
400 VAC
32 A
20–30 minutes
Three phase - 43 kW
400 VAC
63 A
20–30 minutes
Direct current - 50 kW
400 - 500 VDC
100 - 125 A
Battery swapping
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